Starting device, particularly for internal combustion engines



W. PABST April 8; 1941.

STARTING DEVICE, PARTICULARLY Fon INTERNAL CouBUsTIoN ENGINES 2 Sheets-Sheet l aval w ML Filed Jun 1o, 1958 ff W pril 8, 1941. w, PABST 2.237.970

"STARTING DEVICE, PARTICULARLY FOR INTERNAL COIIBUSTIONENGINS Filed June 10, 1958 2 Sheets-Sheet 2 ntenied Apr. 8, 19.41

STARTING DEVICE, PARTICULARLY FOR INTERNAL CGMBUSTION ENGINES Wilhelm Pabst, Hamburg, Germany Application June 10, 1938, Serial No. 213,102 ln Germany June 25, 1937 (Cl. )Z1- 37) and closed'l end of the driving sleeve 2i. This 3 Claims.

The invention refers to starters for internal combustion engines, and in particular tostarters that cari be fed by some means of pressure. such as air orgas. from `a pressure chamber or. an explosive cartridge.

The required starting moment is effected by a piston moving axially, which displaces veither two 'sleeves each provided with inside spiral riiling or one sleeve with inside and another with outside spiral rifling, whereby the inner riiiing with smallest average diameter works in co-operation with a suitably rifled shaft attached to the bottom of the cylinder, the second riflng ol the piston being engaged with a suitably riiied driving shaft or sleeve that bears at its front end the coupling teeth for the starting claw.

lin the accompanying drawings, like characters of reference indicate like parts in the several views, and:

Figure 1 is a vertical section taken diametri cally through the axis of the device;

Figure 2 is a fragmentary section on the line Zl-2 .of Fig. 1;

Figure 3 is an elevation showing a portion of the piston stem;

Figure 4 is an axial section through Fig. 3;

Figure 5 is-a side elevation of a carrier or inteirnediate sleeve used herein; and

Figure 6 is an axial section through Fig. 5.

lhe action in this case is as follows:

The piston i, which is firmly connected with the sleeve 29 provided with inside and outside rifiing 26 and 21, respectively, slides on the one hand on the inner guide surface of the cylinder il and on the other hand on the cylindrical part ci the axially arranged shaft Iiv which is rigidly connected to the head of the cylinder. The tree end of the shaft 6 is reduced and has keyed thereon for longitudinal sliding movement a cylindrical carriage 29. A.plug 39 closes the free end of shaft ii and provides a flange 30a to limit the .sliding movement of the carriage 29 in one direction. Movement of the carriage 29 in the other direction is limited by the shoulder 29a at the inner end of the reduced portion of shaft il. The outer surface of carriage 29 is provided with rifling 2B which is in constant mesh with the inner rifiing 2G of the sleeve 20. A driving sleeve il is slidably and rotatably mounted in the lower end of the casing Il, the amount of sliding being limited by stops 3|, 3x2, 33 to correspond to the' amount of sliding permitted carriage 29. A torsion spring 94 has one end connected to the member Ml carried by the stationary shaft 6 and has its other end connected as at to the lower springis torsioned during-I downward movementy of the piston and actsto assist in restoring the member 2| to its normal position upon upward movement of said piston. keyed to they shafti as ais-3B. plain the operation of the device, theshaft 6 is rigidly,mounted witliih the outerncasing 4 and isnot rotatable. In casing 4, guided through part 6, the piston tI can then slide with its sleeve 20 both in longitudinal direction as well as by means of a rotating movement.' At first the sleeve 20 can only move in '.a longitudinal direction at the time when forces affect the head of the piston I, said forces pressing `downwardly because the carriage 29 slides longitudinally `along the guide shaft B and is not rotatable thereon. The pressure on the piston I can at first move sleeve 20 and carriage 29 downwardly until the latter reaches collar 30a of the plug 390i' guide shaft 6 and contacts it. This stops automatically the longitudinal movement, and piston I can only further yield to the pressure and continue a downward movement when'the, thread 26 of the piston I'rotates on the thread 28 of the guide carriage 29. Only at this moment does a rotating movement of the piston I occur.

The effect -of the device will then be as follows:

The action on the piston I may be causedby the pressure gases entering at l. When the pis ton has then been brought in the above stated manner to the rotating point, by which also sleeve 20 rotates, which has the outer riing 21,\ the rotating movement is transmitted to the driving sleeve 2| whose rifling 25 engages rifling 21. This gives driving sleeve 2| any desired number of rotations for each stroke of piston I in accordance with the pitch selected for the rifiing.

When piston I has passed ports I2, the pres sure gases escape into the open air and spring I4 of the valve I5 opens the valve which also permits the escape of gases. The return of piston I to the rest position shown in the drawings is then caused by pressure spring I6 and the operation is complete. The pressure gases entering at I drive the piston forward, whereby the piston slides awayl from the cylinder head, carrying with it the carriage 29 and driving sleeve 2| until the carriage engages stop 39a. The keyed connection between carriage 29 and shaft 6 prevents rotation of the sleeves 20 and 2| during this movement. When the carriage 29 engages stop 30a, the sleeve 29 of piston I is given The carriage 29 is To further ex.

a twist by the riflings 28 on carriage 29 engaging into the corresponding interior rifling 26 of the sleeve, this twist being in turn transmitted to the driving sleeve 2l. As the driving sleeve 2| is provided with riings 25 which engage into the corresponding outer rifiings 21 of the sleeve 20, the driving sleeve 2lv is given an extra twist in addition to that of piston I, so that by this arrangement the driving sleeve 2|, which bears Yat the other end the coupling teeth 9, can make any desired' number of revolutions during the whole stroke of piston I. The number of revolutions depends solely on the choice of the pitch of the individual riflings.

After having traversed its full stroke during the starting process, piston I uncovers the exhaust ports I2 of shaft 6, so that the pressure gas can escape into the open air through the ports I2 and the bore I3. Owing to the drop of the pressure caused by the opening of ports I2, the spring I4 of the valve I5 comes into predominance and opens the valve I5, so that the consumed gases may also escape through the opening Ha of the valve spring housing Mb and then through the port I4c in the head la of the cylinder 4. Owing to this complete release of the pressure gases the spring I6 is able to take the whole piston I with the sleeve 20 back to its above position of`rest.

Before the piston I reaches its upper position of rest the valve I5 is closed again by the piston striking the stop I9. In a renewed starting process the highly compressed gases then keep the valve I5 closed until a decrease of the gas pressure again takes place through the escape of the gases through the opening I2.

What I claim is:

1. In a starting device of the kind described, a cylindrical casing having a fixed end, a centrally disposed hollow cylindrical guide shaft xed at one end tothe center of the fixed end and projecting toward the opposite end of the cylinder, steeply pitched spiral threads on the free end portion of the exterior of the guide shaft, a piston fitting in said cylinder and having an elongated hub forming a sleeve. said sleeve having internal grooves engaging said threads, a driven shaft actuated by the movement of said sleeve, said guide shaft having a smoothly cylindrical portion extending from the fixed head to said threaded portion to effect smooth guidance of the piston and to prevent escape of gas between the piston and sleeve, and

said ports being uncovered by said piston adjacent the end of the stroke thereof.

2. In a starting device of the kind described,

Ya cylindrical casing having a fixed end, a centrally disposed hollow cylindrical guide shaft xed at one end to the center of the fixed end and projecting toward the opposite end of the cylinder, a guide carriage slidably keyed on the free end of said shaft, means limiting the sliding of said carriage on said shaft, steeply pitched spiral threads on the periphery of said carriage, a piston fitting in said cylinder and having an elongated hub forming a sleeve, said sleeve having internal grooves engaging said threads, a driven shaft actuated by the movement of said sleeve, said guide shaft having a smoothly cylindrical portion extending from the fixed head to said keyed end portion to effect smooth guidance of the piston and to prevent escape of gas between the piston and sleeve, means to limit movement of the piston by pressure of fluid admitted between the fixed head and piston and comprising ports in said guide shaft opening into the hollow interior thereof, said hollow interior opening directly tothe atmosphere, said ports being uncovered by said piston adjacent the end of the stroke thereof, an escape valve ln said fixed head, spring means effecting opening of said escape valve upon passage of the piston to position to open said ports, and means to effect closing of said valve upon movement of the piston to normal position.

3. In a starting device of the kind described, a cylindrical casing, an axially disposed cylindrical guide shaft fixed at one end to one end of said casing and projecting toward the opposite end of said casing, a driving sleeve rotatably fitted in said opposite casing end, a guide carriage slidably keyed on the free end of said shaft, steeply pitched spiral threads on the periphery of said carriage, a hollow piston fitting in said cylindrical casing, an axial sleeve on said piston surrounding said shaft, the inner surface of said sleeve having internal grooves engaging said threads of said carriage, and the periphery of said sleeve having spiral threads, said driving sleeve having internal grooves in constant mesh with said peripheral threads of said first sleeve.

WILHELM PABST. 

